I've eaten at Alka about half a dozen times since my hotel was right next-door. It would be perfectly fine for lacto-vegetarians but vegans should probably steer clear.
When we ordered our dishes without butter, ghee, cream, etc., the wait staff always nodded, but about 2/3 of the time the kitchen failed to leave the dairy products out of our dishes as requested. "But it's only a very small amount of butter," we were told, and even the manager on duty tried to convince us that a little bit was OK. When we tried to explain that we don't take any dairy products at all, they looked at us like we were freshly escaped from the asylum. This happened on at least 3 or 4 different visits, with different staff.
When we investigated, we were told that almost all of the dishes on the menu are prepared with ghee (and apparently can't be made without it). So, our verdict: not at all "vegan friendly." We stopped going to Vega and started going to the excellent Saravana Bhavan, just next-door.
Again, lacto-veggies might well enjoy Vega, but vegans are advised to give it a miss unless you're ready to practically launch a campaign to make sure the waiter understands and communicates your wishes to the kitchen unmistakably, and be prepared to send the dish back if they don't comply.
Cons: No concept of vegan, resistant to preparing food sans dairy